Septic tank drain field and method



Oct. 19, 1965 J. R. THOMPSON SEPTIC TANK DRAIN FIELD AND METHOD Filed Jan. 2, 1962 INVENTOR.

James R. Thompson ATTORNEY United States Patent 3,212,266 SEPTIC TANK DRAIN FIELD AND METHOD James R. Thompson, Morreene Dairy Road, Durham, N.C. Filed Jan. 2, 1962, Ser. No. 163,784 1 laim. (Cl. 6111) This invention is concerned with drain fields designed to accept the liquid efiiuent from septic tanks and distribute the same to the soil. The invention is more specifically concerned with the construction of drain lines forming part of such a field.

In the conventional drain line construction, a long sloping trench the length of the drain line is filled with cinders, gravel or other suitable material through which the liquids can percolate to the soil. Prior to laying in this material, there is customarily installed a series of wooden boards which are laid edgewise end to end from one end of the line to the other. The percolating material is poured into the trench, up to the upper edges of the boards which assume the desired slope or pitch which the line is expected to have. Short sections of spaced tile are placed in the trench so as to lie in end to end relation from one end of the line to the other end on top of the boards upper edges. Suitable caps are placed over the upper portion of each of the spaces between the tiles so as to prevent the spaces from being later filled with debris from above. The trench is then back filled with final layers of fine percolating material and soil to the original grade.

So long as the described slope aligning boards maintain their alignment and the soil is of such nature as to readily accept the liquids coming through the line the septic tank field will generally operate satisfactorily. I have noticed however that problems usually begin to arise in about two or three years when the aligning boards rot out and disturb the initial alignment causing tiles to shift sideways or vertically. At such times the initial drain pattern is lost and portions of the soil will begin to receive more than their share of the efiluent. This in turn causes the liquids to come to the surface of the soil resulting in foul odors and extremely unsanitary conditions.

In addition to the alignment problem, conventional septic line construction also presents another operating problem if the soil in which the line is laid exhibits any tendency at all to resist immediate acceptance of the liquids. This problem is concerned with the fact that when the liquids leave the line through the spaces between the tiles and reach the sides and bottom of the trench they should normally continue to filter on through the surrounding soil. However, when the soil is of such nature as to resist reception of the liquids, I have observed that the trench will act somewhat as a pipe and the liquids due to the slope of the trench will flow to the low end of the trench and if in sufilcient quantity will rise to the surface causing a disagreeable situation at the end of the line. This is particularly evident by the fact that grass is frequently seen to be in abundant supply at the end of a septic drain line as compared to the grass growing above the line at its head.

It is a well-known fact that many rural building areas that would otherwise be suitable for housing are not being utilized due to the lack of a satisfactory sewage disposal system. Some of the rock and extremely hard soils are probably not adaptable to any form of home sewage system. However, it is known that a considerable portion of these building areas have soils that are at best only slightly resistant to liquid acceptance and it is to these latter areas that my invention is especially directed.

In general, my invention has as its object the provision of a septic line method and construction directed to solving both of the operating problems discussed above. As to the aligning problem, my invention provides for the drain line itself to be supported on permanent supports which give the line its slope and which endure for substantially the life of the line itself. As to the problem of the liquids running to the end of the trench, my invention provides for the trench to be broken up into a series of short drain fields that are hydraulically isolated one from the other and that are adapted to hold the liquids received therein until the same either evaporate upwards or dissipate themselves in the soil surrounding the particular short drain field. I accomplish this by installing solid, thin wall dams at given spaced intervals which act to break up the overall line drain field into a series of short hydraulically isolated drain fields and which also provide in one embodiment of the invention a means for supporting relatively long lengths of perforated drain tile so as to maintain a permanent line alignment. In this way, the liquids continue to be substantially evenly distributed for long periods of operation and except for restriction as to lengthwise flow beyond the dams the liquids remain free to fiow upwards and to the sides of the trench. Unlike other prior art approaches to the problems, such as in Benedict Patent 2,637,170 and Dorfman Patent 2,803,948, my construction allows the full dissipating qualities of the trench to be employed both as to upward evaporation and downward and side percolation.

The above and other objects and advantages of the in vention will be seen as the description proceeds. In the drawings:

FIGURE 1 is a perspective of a portion of a septic drain line embodying elements of the invention.

FIGURE 2 is a perspective of one of the in the invention.

FIGURE 3 is an end elevation of the aligning board shown in FIGURE 1.

FIGURE 4 is a perspective of a portion of a septic drain line showing another arrangement of the invention.

FIGURE 5 is a side elevation of one of the relatively long perforated tiles employed in the embodiment of FIGURE 4.

It is Well known that any trade resists change in its traditional methods therefore in FIGURE 1, there is illustrated an embodiment of the invention which most closely follows traditional practice but at the same time embodies the important elements of the invention. In this figure, the dashed line 10 represents the boundaries of the septic line trench. For purposes of simplification, the usual percolating materials such as cinders or gravel and the covering layer of soil is not shown. Within the trench 10 there is periodically spaced at intervals of several feet a series of thin wall, solid dams 11 which extend from side to side of the trench and up to the slope line and break up the trench into a series of relatively short hydraulically isolated drain fields. While these dams may take any of several forms, I have found that a cast concrete or tile block shaped in the form illustrated by FIGURE 2 adequately serves the purpose. When being installed, the dams 11 should be placed in the trench 10 prior to pouring in the percolating materials and each dam should be so located so as to have the curved tile mounting surface indicated at 12 at the height corresponding to the slope of the line at the dams location. While not shown, it will also be found preferable in some soils to caulk the dam with cement at its edges on the upstream side.

Between each of the dams 11 there is located a supporting board 13 preferably made of a permanent material such as concrete or tile and whose length corresponds to the length between each darn or space allowed. That is, the length of these boards defines the length of the short fields. The boards are placed on their edges between the dams, centrally of the trench and in end to end relation. The upper edge of each dams employed board is provided with a curved surface indicated at 14 in FIGURE 3 representing an end elevation view of the board. To equalize hydraulic pressure and liquid dissipation each board is further provided with suitable drain holes 15. Surfaces 14 and 12 once located in the trench so as to define the desired slope of the line thus provide a relatively permanent alignment means and a convenient support for the tiles 16 which are placed in the conventional spaced apart manner. These tiles in their conventional size form a pipe approximating four inches inside diameter. While not shown, it should be understood that a suitable connector cap such as that illustrated in Gutman Patent 2,029,920 is placed between each pair of tiles to provide a protective cover over the drain spaces.

It will be seen from FIGURE 1 that as the liquids leave the various spaces between the tiles they will be compelled to remain in between the particular dams between which the spaces are located thus insuring a more uniform distribution over the line of which the tiles are a part. Before any lengthwise fiow down the full length of the trench can take place the liquids will at least have to rise to the upper edges of the dam as represented by the surfaces 12 and 17. It will be seen however that the liquids continue to remain free to fiow to the sides and bottom of the trench as well as upwards which gives maximum utilization o fthe trenchs dissipating qualities. With the aligning boards being made of a permanent material and the curved surfaces along the upper edges of the boards acting to control sideways shift of the tiles, any tendency to lose the original alignment is thereby minimized. From an overall construction viewpoint therefore, it will be seen that with relatively simple changes in the conventional methods, radically different operating characteristics are achieved.

Another form in which the invention may be constructed is illustrated by FIGURES 4 and 5. In this embodiment, need for the supporting boards 13 is eliminated by employing a perforated pipe which is actually supported by the dams themselves and extends over the spaces between the dams. The pipe 18' for example may be extruded of suitable materials in sufficient length to bridge the space between adjacent dams. For purpose of allowing the liquids to leave the pipe at intervals, pipe 18 is provided with suitable slots 19 and is also provided with suitable male and female ends indicated at 20, 21 respectively. With this construction, the respective curved surfaces 12 of each of the dams 11 are located so as to define the line slope and then the various lengths are joined together and supported on these surfaces. This manner of carrying out the invention involves less installation time and a fewer number of components. For these reasons it is believed to be the preferred embodiment and it will be understood that .the operation is essentially the same as with the first embodiment except in the manner of supporting the line.

In summary, the method and construction taught by the present invention allows the liquids to be received in a series of relatively short hydraulically isolated drain fields whose ends are defined by the referred to dams, whose bottom and sides are defined by the boundaries of the trench and whose upper surface is confined only by the back fill materials of the line. The liquids are thus confined lengthwise but remain free to move down, sidewise and upwards. Permanent alignment .of the line is assured through utilization of the dams as support in the one embodiment and in utilization of permanent alignment boards extending between the dams as the supporting means in the other embodiment.

Having thus described my invention, what I claim is:

In a septic tank drain line including an absorption trench and sectional liquid drain pipe of substantially smaller cross section extending the length thereof; a plurality of imperforate vertical walls spaced at uniform intervals along the length of said trench and extending crosswise thereof, said walls acting to dam said trench ateach location thereof below the slope line of said pipe and each said wall having a central curved portion supporting and aligning said pipe; a series of per-- forated permanent elongated support members located on their bottom edges centrally of said trench between each pair of said walls and having longitudinally extending transversely curved portions in their top edges supporting and aligning said pipe, said walls being effective to establish a series of hydraulically isolated drain fields, said members defining the length of said fields and said curved portions of said members and walls defining the slope of said line, the bottoms tops and sides of said fields being defined by the boundaries of said trench and the ends by said walls thereby blocking lengthwise flow while maintaining downward, side and upward flow in each of said fields.

References Cited by the Examiner UNITED STATES PATENTS 659,452 10/00 Pfouts 210-151 968,225 8/ 10 Ziller 16-13 1,852,268 4/32 Schmidt 61-35 2,637,170 5/53 Benedict 61-11 2,767,801 10/56 Eads 61-11 X 2,782,604 2/57 Mixon 61-11 2,795,542 6/57 Home et al. 61-11 X 2,803,948 8/57 Dorfman 16-11 2,866,319 12/58 Nicholson 61-11 OTHER REFERENCES Handbook of Drainage and Construction Products, published by Armco Metal Products, 1958, pp. 441442.

5 CHARLES E. OCONNELL, Primary Examiner. 

